The uninhabited island volcano in south-central Alaska erupted twice Friday night and twice Saturday morning, following 10 days of relative calm, scientists with the U.S. Geological Survey said.

The first eruption was the largest, lasting nine minutes, said research geologist Jim Vallance. The blast occurred at 8:12 p.m. Friday, flinging a cloud of ash almost six miles into the air.

"It tapered off afterwards," Vallance said.

A smaller eruption occurred at 11:37 p.m., lasting about three minutes

The third eruption occurred at 2:04 a.m. Saturday, sending a plume up more than five miles. It lasted two minutes, but continued to vent ash for an hour, Vallance said.

By the time the fourth and final eruption occurred at 7:42 a.m., a cloud cover had shrouded the volcano, making it difficult to gauge ash activity, according to Vallance.

"We think it was similar to the third one," he said, adding the volcano had calmed since then. "Further explosive eruptions could occur through the day with little warning."

The eruptions spread a yellowish haze to the southeast and left a light ash cover at a salmon hatchery on Afognak Island 100 miles from the volcano. John Mahan, assistant manager of the Kitoi Bay Hatchery, said the layer was minimal and posed no immediate risk to fish in outside holding tanks.

"There's a little light gray on the snow, like city snow gets from exhaust," Mahan said. "It's such a light amount, there's no danger now, unless another major eruption sent out a measurable amount. Then we could put tarps over the fish."

Traces of ash also were reported in the town of Kodiak about 120 miles southeast of Augustine, said geologist Jennifer Adleman.

Gary Carver, an independent geologist who lives just outside the city, said he drove around the area north of town Saturday and could see the tip of the ash cloud and minute dark fragments in sections of clean snow.

"It's not detectable to most people, just a few tiny scattered flecks of material," he said. "You almost need a magnifying glass to see them. But I've looked at ash many times and its characteristic appearance is like a broken light bulb."

Vallance said scientists would fly over Augustine later Saturday, weather permitting.

The explosions prompted weather service officials to issue an ash fall advisory for Kodiak Island to the southeast and a warning for pilots in the area. Alaska Airlines canceled six flights from Seattle, Portland, Ore., and Los Angeles Friday night, but resumed service Saturday morning, said spokeswoman Caroline Boren.

The latest eruptions were similar in size to major explosions in mid-January that dusted the Kenai Peninsula with a coat of ash, scientists said.